Insect Growth Regulators: Some Effects of Methoprene and Hydroprene on Productivity of Several Stored Grain Insects.

Abstract

The effects of two insect growth regulators on the productivity of Rhyzopertha dominica, Sitophilus oryzae and S. granarius were studied by exposing insects to wheat treated with methoprene (isopropyl 11-methoxy-3,7,11-trimethyldodeca-2,4-dienoate) or hydroprene (ethyl 3,7,11-trimethyldodeca-2,4-dienoate) at concentrations of 1, 5, 10 and 20 ppm. Parental adult mortality was generally higher on wheat treated with methoprene than with hydroprene, and this effect was usually enhanced under unventilated conditions. The productivity of the three species was markedly reduced, in some instances suppressed, under unventilated conditions, whereas only R. dominica productivity was depressed under ventilated conditions. When progeny were produced, their productivity was, in general, lower than normal.

Effect of temperature and grain type on the long‐term persistence and efficacy of s‐methoprene in controlling Rhyzopertha dominica

“…Several studies have revealed that pest exposed on different surface substrates treated with methoprene markedly affected the efficacy of methoprene . The source or specific formulation of methoprene, application methods or environment conditions may also result in different efficacies . Thus, one of the factors must have induced the difference in our studies.…”

“…Although the trend in our results was similar to that of Samson, the application rates of methoprene were obviously different. Numerous researchers have also shown that methoprene caused >99% suppression of F 1 R. dominica at application rates of 1, 2 or 5 mg kg ‐1 . Mian and Mulla reported that methoprene applied at 1 mg kg ‐1 caused complete inhibition of progeny on wheat and maize for 10 months at 27 °C, and no significant differences were found between the two grains.…”

“…IGRs can also be applied to grain as protectants, given that these chemicals exhibit reduced application risk and environment pollution compared with neurotoxic insecticides . Methoprene, a juvenile hormone analog that can be used as a protectant and acts as an IGR, has been shown to reduce progeny production in several stored grain pests, especially R. dominica …”

“…Previous studies have found that the efficacy of methoprene varies with surface substrate, application method and environmental conditions . Wijayaratne et al evaluated the efficacy of methoprene in controlling Tribolium castaneum at different temperatures on two surface substrates.…”

Activity of a juvenile hormone analogue as a protectant against the lesser grain borer, Rhizopertha dominica (F.) (Coleoptera: Bostrichidae)

“…The fact that this JHA was not ovicidal could have been due to the dosage used, because pyridyl ethers have been found to be ovicidal at higher dosages (Kramer and McGregor, 1978). Hoppe (1976), Amos and Williams (1977) and Kramer and McGregor (1978) reported that insects that developed within the kernels (internal feeders), may be relatively less susceptible to JHAs because of insufficient amounts of these compounds reaching the endosperm where the immatures of these pests are. Rowlands (1976) demonstrated that JHAs applied to whole wheat kernels were found mainly in the aleurone layers of the grains and hardly at all in the endosperm.…”